Drill collar



March 1, 1966 w. E. SCARBOROUGH 3,237,427

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United States Patent 3,237,427 DRILL COLLAR William E. Scarborough,Houston, Tex., assignor to Reed Roller Bit Company, Houston, Tex., acorporation of Texas Filed July 29, 1963, Ser. No. 298,277 10 Claims.(Cl. 64-1) This invention relates generally to deep well drilling toolsand more particularly to a drill collar for use in a rotary drillingstring.

Drill collars are used in drilling strings to concentrate a weight loadon a drilling bit at the lower end of the string. A drill collarcomprises a long and heavy member connectable in the string immediatelyabove the bit, and has a longitudinal bore therethrough for conductingdrilling fluid to the bit. Two or more collars may be used in tandemdepending upon the desired weight to be applied to the bit. Drillcollars having cross-sectional shapes which are substantially squarehave come into use in the rotary drilling of wells, as one means ofcontrolling hole deviation. Such drill collars usually have aconfiguration wherein the corners have been somewhat rounded, and areused to stabilize or guide the bit so that the hole may be substantiallyvertical and to prevent sharp deviations of the bore hole being drilled.The diagonal distance across the square section corners is made tosubstantially conform to, or is made a fraction of an inch under, thediameter of the bore hole. If, as is usually the case, the ends of thesquare drill collar are machined to provide cylindrical tong space, thenof course the square section of the collar will be somewhat remote fromthe bit, and lateral components of force on the bit and the end of thecollar may cause the bit to deviate from its path. With the collar ofthe invention, a drill collar is provided which has a substantiallysquare cross-sectional portion adjacent the bit, and has a cylindricalportion remote from the bit, to accommodate pipe wrenches or tongs usedin screwing the collars together or in unscrewing them.

It is a general object of this invention to provide a new and improveddrill collar for use in a drilling string.

Another object is to provide a new and improved drill collar which willstabilize and guide a drilling bit during the drilling operation.

Another object is to provide a drill collar having generally asubstantially square cross section wherein a portion of saidsubstantially square cross section is immediately adjacent the drillingbit, and wherein a cylindrical tong portion is provided somewhat removedfrom the drilling bit.

Another object is to provide a new and improved drill collar whichguides and stabilizes the string in the hole and yet provides for thefree passage of drilling fluid thereby.

Other objects will become apparent from the following description andthe accompanying drawings, in which:

FIG. 1 is a side elevation of the drill collar of the invention shownpartly in section.

FIG. 2 is a cross-sectional view taken along lines 22 in FIG. 1.

FIG. 3 is a cross-sectional view taken along lines 33 in FIG. 1.

FIG. 4 is a diagrammatic view showing the drill collar and a drillingbit in position in a bore hole.

FIG. 5 is a cross-sectional view taken along lines 5-5 in FIG. 4.

Referring to the drawings, a rotary drill collar is shown generally at11, and may be provided with threaded boxes 12 at the ends thereof forattachment to another drill collar, to a lower end of a drill pipestring, or to a drilling ice substitute or adapter which is attached toa drilling bit. A bore 13 extends longitudinally through the collar toprovide for communication of drilling fluid therethrough, as is wellknown.

The drill collar 11 may have a generally square cross section throughoutmost of its length with flats 15 and corners 16, which, as illustrated,may be rounded. The upper end of the drill collar 11 may be providedwith a portion 17 which is generally cylindrical in shape. Thecylindrical end 17 is provided so that the collar may be grasped by apipe wrench or tongs in order to screw or unscrew it from another collaror from the rest of the parts in a drill string. The lower end 18 of thedrill collar is generally square in cross-sectional shape as is shown inFIG. 3.

Since the flats 15 provide for adequate return passage area for thecirculating fluid, between the drill collar and the wall of the borebeing drilled, the corners 16 of the drill collar may extend radially toa position where they almost touch the walls of the bore hole, therebylaterally stabilizing the drilling bit in its rotary operation so that amore nearly vertical bore hole may be produced, having fewer sharpdeviations or dog legs.

As may be seen in FIGS. 4 and 5, the drill collar 11 is attached to adrilling bit 19 shown in operating position at the bottom of a borehole. The drill collar 11 may have a cylindrical portion 20 providedthere-on which is somewhat removed from the drilling bit 19. Thecylindrical portion 20 is provided so that the drill collar may begrasped with a pipe wrench or tongs in order to screw or unscrew it ontoor from the drill bit or from another member in a drilling string. Aswill be apparent, the lower, square cross-sectional portion 18 of thedrill collar is immediately adjacent the drilling bit, and in thisposition, it affords a stabilizing influence close to the drill bit sothat the drill bit 19 is not easily laterally deflected from its path.Since the corners 16 of the collar extend substantially to the diameterof the bore hole being drilled, it will be apparent that substantiallateral stabilization for the bit is afforded, and further, the flats 15of the collar provide with the wall of the bore hole, adequate area forthe return of drilling fluid and cuttings dislodged by the drill bitupwardly thereby to the surface of the earth.

In the rotary drilling of deep wells, the formations penetrated by thedrill bit are frequently composed of alternate hard and soft layerswhich may be disposed or bedded in planes at an angle other than normalto the direction of drilling. This condition, coupled with the tendencyof the drill collar to buckle under compressive loads, may result indeviation of the bore hole from a desired path. The square drill collarof the invention effects a stiffening and centering of the lower end ofthe drilling string, immediately adjacent the drill bit, to alleviatethe tendency of the bit to deviate from the established center of thehole previously drilled.

Thus the invention provides a drill collar having a generally squarecross-sectional shape or configuration, and provides for the employmentof such cross-sectional shape immediately above the drilling bit inorder to alleviate the tendency of the drilling string to driftlaterally during rotation thereof. The cylindrical portion 20 beingsomewhat more flexible than the square section of the drill collar isdisposed in a position remote from the bit rather than immediatelyadjacent to such bit. The cylindrical portion 20 of the drill collar isformed at regular tong height to accommodate rotary tongs. Thus a collarhaving a new and improved use, and having a practical configuration isprovided whereby such drill collars may be employed in the drilling ofdeep wells with standard rig equipment since no special tools arenecessary to handle the square drill collar provided by the invention.In other words the corner portions of the drill collar may bear on thewall of the bore hole immediately above the drill bit as the drillstring is rotated during the regular drilling operation, and thus willresist the tendency of the bit to deviate from its path, and thecylindrical portion, which does not provide sufficient lateralstabilization for the bit but is necessary for the accommodation oftongs, is somewhat removed from the drill bit.

This invention is not limited to the embodiment shown. Various changeswithin the scope of the following claims will occur to those skilled inthe art.

What is claimed is:

1. A drill collar connectable at its upper end into a rotary drillstring, and connectable at its lower end to a drilling bit, said drillcollar having a substantially square cross-sectional portion withrounded corners immediately above said bit, and having a generallycylindrical crosssectional portion spaced from said drilling bit, thesaid square portion having a diagonal dimension substantially the sameas the diameter of the drilling bit.

2. A drill collar connectable at its ends into a rotary drill string,and having a portion substantially square in cross-section immediatelyadjacent the lower end thereof, and a cylindrical portion extendingupwardly from said square portion, the corners of said square portionbeing effective to laterally stabilize the drill collar as the drillstring is rotated in a bore hole.

3. An elongate member, suitable for connection into a rotary drillingstring for drilling a well bore, and having a fluid passageway extendinglongitudinally therethrough, the lower end of said member beingsubstantially square in cross-sectional shape, the said member having asubstantially cylindrical portion above said square sectional portionadapted to be engaged with rotary tongs for screwing and unscrewing themember into and out of said rotary drill string, the corners of saidsquare lower end being disposed so that they are in close proximity tothe wall of the well bore during drilling operations,

4. A drill collar connectable at its ends into a rotary drill string,and having a bore extending longitudinally therethrough, said drillcollar having a substantially square cross-sectional shape with roundedcorners at the lowermost end thereof and having a first cylindricalportion above said lower end, and a second substantially squarecross-sectional shape adjacent the upper end of said first cylindricalportion, and a second cylindrical portion adjacent the upper end of saidcollar, the corners of said square portions being effective to laterallystabilize the drill collar as the drill string is rotated in a borehole.

5. A drill collar having a fluid conducting means extendinglongitudinally therethrough, the upper end of said collar beingsubstantially cylindrical in cross-sectional shape, the lowermost end ofsaid drill collar being substantially square in cross-sectional shape, asecond portion of said drill collar being substantially cylindrical incross-sectional shape immediately above the said lower cross-sectionalshaped portion, the said drill collar being substantially square incross-sectional shape between said upper cylindrical portion and saidsecond mentioned cylindrical portion.

6. An elongate drill collar member having a generally squarecross-sectional shaped portion at the lowermost end thereof, and agenerally cylindrical cross-sectional portion adjacent said lower squareportion, and a generally square cross-sectional shape extending from thesaid cylindrical shape longitudinallyupwardly of said collar, and asecond cylindrical portion adjacent the upper end of said collar.

7. A drill collar having a fluid conducting means extendinglongitudinall therethrough, the said drill collar having two portionsgenerally square-shaped in cross section, the first square portion beinglocated immediately adjacent the lower end of said collar, the collarhaving a portion cylindrical in cross-section immediately above saidfirst square section portion, the said second square cross-sectionalportion of the collar being located above said cylindrical portion.

8. A drill collar having a fluid conducting means extendinglongitudinally therethrough, and having two portions substantiallysquare in cross-sectional configuration, the first cross-sectionalportion of the collar being located immediately adjacent the lower endthereof, the said collar having a cylindrical portion adjacent saidlower square portion, the second square portion of said collar extendingupwardly from said cylindrical'portion.

9. A drill collar having first and second square shaped portions, thefirst square portion being located adjacent the lower end of saidcollar, and the second square portion being located remote from thelower end of said collar, and a cylindrical portion extending betweensaid first and second square portions.

10. A drill collar having a first portion substantially square in crosssection adjacent the lower end thereof, and a second portionsubstantially cylindrical in cross section adjacent the upper end ofsaid first square portion, and a third portion substantially square incross section adjacent the upper end of said secondcylindrical portion.

References Cited by the Examiner UNITED STATES PATENTS 2,199,738 5/1940Bowles l-320 2,281,952 5/1942 Ransone et a1. 7532O 2,693,345 11/1954Martin et a1 320 OTHER REFERENCES The Oil and Gas Journal, March'19,1962, published by Petroleum Publishing 00., Tulsa, Oklahoma, pages177-178 relied on.

BROUGHTON G. DURHAM, Primary Examiner.

ROBERT C. RIORDON, Examiner.

1. A DRILL COLLAR CONNECTABLE AT ITS UPPER END INTO A ROTARY DRILLSTRING, AND CONNECTABLE AT ITS LOWER END TO A DRILLING BIT, SAID DRILLCOLLAR HAVING A SUBSTANTIALLY SQUARE CROSS-SECTIONAL PORTION WITHROUNDED CORNERS IMMEDIATELY ABOVE SAID BIT, AND HAVING A GENERALLYCYLINDRICAL CROSS-